The invention relates to an integrated circuit, having an external and an internal supply terminal and a voltage converter which is connected between said terminals in order to apply a voltage to the internal supply terminal which is lower than that present on the external supply terminal.
An integrated circuit of the kind set forth is known from 1987 IEEE International Solid-State Circuits Conference, Feb. 27, 1987, SESSION XIX: HIGH DENSITY SRAMs, FAM 19.2: A256K SRAM with On-Chip Power Supply Conversion, Alan L. Roberts et al., pp. 252-253.
The integrated circuit known from the cited publication comprises not only said voltage converter but also a detector which detects whether a standard supply voltage of 5.0 V is present on the external supply terminal or a lower supply voltage, in this case 3.3 V. The know integrated circuit also comprises a switching circuit with two electronic switches which are controlled by the detector. A first electronic switch can directly connect the external and the internal supply terminal, while the second electronic switch can connect the voltage converter to the external and the internal supply terminal. When the detector detects an external supply voltage of 3.3 V, the detector turns on the first electronic switch and turns off the second electronic switch. When the detector detects a standard supply voltage of 5 V, the reverse takes place, i.e. the first electronic switch is turned off and the second electronic switch is turned on. Thus, when a standard supply voltage of 5 V is applied to the external supply terminal, the detector and the switching circuit of the known integrated circuit may be assumed to be absent and the input of the voltage converter may be assumed to be connected to the external supply terminal.
The voltage converter of the known integrated circuit comprises an active voltage divider, with an analog circuit which has the drawback that oscillations could occur therein.